Sea changes: A woman collects food from the sea, an important activity for people living along the coast from South Africa
to Somalia. (Garth Cripps)
‘We have to alert the world to the impending food security, livelihoods and marine ecosystems disaster in the Western Indian Ocean, which extends from South Africa all the way up the east coast of Africa. We probably have about 15 years before things get very serious. It is not a lot of time if you think about how slowly things move in terms of politics.”
These are the words of Mike Roberts, head of the South African Research Chairs Initiative in Ocean Science and Marine Food Security, hosted by Nelson Mandela University, the University of Southampton and the Southampton-based National Oceanography Centre in the United Kingdom. He is also the recipient of the 2020 Newton Prize, worth R4-million.
He said research shows that the Western Indian Ocean is warming faster than any other ocean.
“Sixty-million people depend on the ocean for food and livelihoods, and fish abundance projections clearly demonstrate that the amount of fish in the region, as well as species diversity, is rapidly declining as a result of overfishing, ocean warming, pollution and population growth. We are looking at widespread starvation in the Western Indian Ocean by 2035.”
With money from the Newton prize, his team has retrieved five of the seven underwater temperature recorders that Roberts deployed off the Mozambique coast 20 years ago. These have recorded hourly water temperatures over this period.
Roberts says the data from the recorders as well as satellite data clearly shows that the resource-rich Mozambique channel is warming. Northern Mozambique, for example, is on course to heat up by 5°C by 2100. This will devastate the coral reef system and the ecosystems that depend on it.
Roberts and his team are facilitating joint planning and mitigation measures with the Mozambican government.
A Memorandum of Understanding is in place between Nelson Mandela University and the Mozambican government for assistance in building research capacity in ocean science and fisheries.
The models the researchers use further show that, by 2035, the tropical Western Indian Ocean’s marine heatwaves that would normally last from a few days up to about 10 days will extend for far longer periods, at times spanning 12 months.
Roberts said the marine heatwaves inhibit the upwelling of nutrients from the deep to the upper layer where phytoplankton — the base of the marine food web — production takes place.
The research on marine ecosystems in the Western Indian Ocean includes Madagascar, Kenya, Tanzania, Mozambique and South Africa. “To find solutions to address the Western Indian Ocean’s problems requires intensive transdisciplinary, global research,” says Roberts.
The research chair initiative has established the Innovation Bridge and Regional Hub Network, which builds research partnerships between institutions in Africa and the Global North. Another bridge the chair has established is with leading French marine research institutions.
The Ocean Science Campus at Nelson Mandela University forms the principal southern footprint of the innovation bridge in partnership with Rhodes University.
A role of the chair is to increase the number of master’s and PhD students in ocean sciences in Africa.
South Africa’s Agulhas Bank is the widest shelf area on the African continent and supports the chokka/squid fishery. This research, undertaken by the Solstice project, funded by the UK Global Challenges Research Fund, looked at why the squid fishery collapsed in the Eastern Cape in 2013, when more than 2 500 squid fishers lost their livelihoods, affecting about 35 000 family dependants, and whether it can happen again.
Somalia. A mooring is deployed on the Madagascar Ridge seamount, south of Madagascar, to collect important temperature and current data. (Mike Roberts)
Roberts said research shows a shift in the Agulhas Bank ecosystem, probably as a result of climate change.
A research project with French institutions in KwaZulu-Natal called Cyclops is looking at where cyclonic eddies and turbulences in the Agulhas Current affect the coastal ecosystems between Port Alfred and Durban.
“These eddies appear to drive the ocean productivity on this narrow shelf, supporting a huge amount of biodiversity, including many species of fish on which coastal communities rely, as does the commercial fishing sector,” Roberts explains.
The Agulhas Current is showing signs of change and this will probably affect the productivity of the Eastern Cape and KwaZulu-Natal coastal ecosystems. One of these is the annual sardine run.
Roberts hypothesises that the strength of the sardine run depends on the behaviour of eddies and turbulence passing Waterfall Bluff near Port St Johns. Here, the shelf becomes narrow and the northward migrating sardines get stuck if there are no eddies to open “a gate” for them to swim along the shelf to KwaZulu-Natal.
Roberts’ team is also looking at the possible loss of fish larvae from the shelf caused by eddies. Large eddies passing the Thukela Bank can remove the water column from this shelf, and with it all the fish larvae essential for fisheries recruitment. A worry is whether this happens more frequently with climate change.
The team’s research off Kenya and Tanzania has shown how upwelling will diminish in the future there and will harm artisanal fisheries supporting coastal and island people.
“We now need to figure out if this will happen more often in the future,” says Roberts. “Our modelling studies show that this region will heat up by 5°C and that all fish stocks will be seriously low by 2100.”
Another research project focused on three submarine seamounts around Madagascar. Roberts says the seamounts — huge reef systems — are important for marine food security. This is where many of the large pelagic fish are found, such as tuna, as well as the deep-living orange roughy.
Results from this research are being used to involve international bodies to try to protect this area from foreign fleets plundering fisheries at these seamounts because no country owns them. They are in the open ocean and classified as Areas Beyond National Jurisdiction. They have been plundered since the 1970s by several nations, including France, Russia and Asia, and since the 1990s by fisheries operating out of Reunion.
Added to this is the emerging threat of mining. This brings into focus bodies such as the International Seabed Authority. These threats also raised questions about the legal status of seamounts both in and beyond national jurisdiction.
Says Roberts: “Western Indian Ocean governments and the international community urgently need to collaborate on understanding the rate at which changes are manifesting and, critically, mitigation measures have to happen.”